An automotive vehicle internal combustion engine has a flywheel attached to an end of a crankshaft. The flywheel is coupled to the vehicle's drivetrain to propel the vehicle. In certain vehicles, trucks for example, the engine powers not only the drivetrain and but also one or more special-purpose accessories. An example of such an accessory is a fluid power system that includes a hydraulic pump that is driven from the engine through a power take-off.
A power take-off, sometimes referred to as a PTO, is driven by the engine crankshaft, but the power take-off point is typically other than at the flywheel. In certain trucks the flywheel is at the rear of the engine and the PTO at the front. A truck chassis may provide a platform behind a truck cab. The truck may carry certain equipment on that platform, and such equipment may include fluid power equipment. A truck that collects and hauls certain types of waste, such as trash, may have a waste collection body mounted on its chassis behind the cab and containing fluid power equipment, such as a hydraulic powered ram for occasionally compacting the collected trash within a bin of the body. Such a ram may comprise one or more hydraulic cylinders that is or are coupled by a fluid power control system to a hydraulic pump that is driven from the engine through a PTO.
In certain trucks an engine throttle control input sets an engine control to run the engine at a desired engine speed within an engine speed range extending from engine idle speed. The engine control may be designed however such that occurrence of any of certain conditions of vehicle operation will act to override the throttle control input by discontinuing running of the engine at the set engine speed. Rather than shutting down the engine, such events result in the engine being throttled down toward idle speed. The engine can again be reset to run at a desired running speed once all events that would otherwise discontinue speed-set running have ceased. An event that may trigger discontinuance of engine running at a set engine speed is the application of a service brake for decelerating the vehicle.
In certain trucks, it may be desirable to disallow operation of an accessory that is driven through a PTO if the truck is being operated above a certain vehicle speed. However, when the vehicle's transmission is placed in a neutral gear, engine power is not needed to propel the vehicle, and in that case, operation of the accessory should not necessarily be disallowed.
The present invention relates to a circuit for interfacing a vehicle drivetrain, service brake, and power take-off with an engine control: that allows an engine throttle control input to run the engine at a set engine speed, provided that certain events calling for discontinuance of such running do not occur; that allows an accessory to be driven from the engine through a PTO when the vehicle transmission is in a non-neutral gear and the vehicle is being driven at a vehicle speed not exceeding a certain limit; that disallows application of a service brake of the vehicle from discontinuing running of the engine at set engine speed, provided that the vehicle is being driven at a vehicle speed below the desired limit; and that allows the accessory to be driven from the engine through the PTO without discontinuing running of the engine at set running speed when the transmission is in a neutral position.
One general aspect of the invention relates to an automotive vehicle comprising: a combustion engine having a power shaft for delivering torque both to a drivetrain, including a transmission, that propels the vehicle and to an accessory transported by the vehicle; an engine control for running the engine at an engine running speed set by a throttle control input; a brake for selectively decelerating the vehicle; and a circuit interfacing the brake, the drivetrain, and the accessory with the engine control. The circuit comprises a first input that is selectively operable to select between placement of the accessory in driven relationship to the power shaft and placement of the accessory in non-driven relationship to the power shaft, a second input that distinguishes between the transmission being in a neutral position and in a non-neutral position, a third input related to vehicle speed, and a fourth input for distinguishing between application and non-application of the brake. The circuit further comprises a first circuit device that is selectively operable to first and second operating conditions, a second circuit device that is selectively operable to first and second operating conditions, and a third circuit device that is selectively operable to first and second operating conditions. A first circuit connection places the operating condition of the first circuit device under control of the first input, a second circuit connection places the operating condition of the second circuit device under control of the second input, a third circuit connection places the operating condition of the third circuit device under control of the operating condition of the first circuit device, of the operating condition of the second circuit device, and of the third input, and a fourth circuit connection places the engine control under control of the third circuit device and of the fourth input for disallowing application of the brake from discontinuing running of the engine at running speed set by the throttle control input whenever there is concurrence of the first input selecting placement of the accessory device in driven relationship to the power shaft, of the second input distinguishing that the transmission is in non-neutral position, and of the third input indicating vehicle speed is below a certain limit.
Another general aspect of the invention relates to a circuit for interfacing the brake, the drivetrain, and the accessory with the engine control. The circuit comprises a first interface connection for receiving an input that distinguishes between placement of the accessory in driven relationship to the power shaft and placement of the accessory in non-driven relationship to the power shaft, a second interface connection for receiving an input that distinguishes between the transmission being in a neutral position and in a non-neutral position, a third interface connection for receiving an input related to vehicle speed, and a fourth interface connection for receiving an input that distinguishes between application and non-application of the brake. Still further the circuit comprises a first circuit device that is selectively operable to first and second operating conditions, a second circuit device that is selectively operable to first and second operating conditions, and a third circuit device that is selectively operable to first and second operating conditions. A first circuit connection places the operating condition of the first circuit device under control of the input received at the first interface connection, a second circuit connection places the operating condition of the second circuit device under control of the signal received at the second interface connection, a third circuit connection places the operating condition of the third circuit device under control of the operating condition of the first circuit device, of the operating condition of the second circuit device, and of the signal received at the third interface connection, and a fourth circuit connection places the engine control under control of the third circuit device and of the input received at the fourth interface connection so that when installed in the vehicle, the circuit will disallow application of the brake from discontinuing running of the engine at running speed set by the throttle control input whenever there is concurrence of the input at the first interface connection selecting placement of the accessory device in driven relationship to the power shaft, of the input at the second interface connection distinguishing that the transmission is in non-neutral position, and of the input at the third interface connection indicating vehicle speed is below a certain limit.
The foregoing, along with further aspects, features, and advantages of the invention, will be seen in this disclosure of a presently preferred embodiment of the invention depicting the best mode contemplated at this time for carrying out the invention. This specification includes drawings, now briefly described, followed by detailed description that will make reference to these drawings.